Railway braking apparatus



Feb. 2, 1932. c. E. BURNS I RAILWAY BRAKIN? APPARATUS 2 SheetsSheet 1 NMQ WQK S :m w o is Q I: n R .W k 9 R w m Kw B A mm mm HERE mg a T wsfi ws m6 Q V Y m a ESWMWK E @EQ Q WN Q Feb. 2, 1932. 0. El BURNS RAILWAY BRAKING APPARATUS Filed Nov. 28, 1928 2 Sheets-Sheet 2 DNVENTOR 1 G. E. B B

Y ca ac'l M ATTORNEY Patented Feb. 2, 1932 CHARLES BURNS,

Ares

Pr ice 031 IQR Fh'EiT 'HILLS, PENNSYLVANIA, ASSIGNOR'TO THE UNION PENNSYLVANIA RAILWAY BRAKING APPARATUS Application filed Novemherfifi, 1928. Serial No. 322,505.

My invention relates to railway braking apparatus, and particularly to apparatus of the type comprising trackway mechanism adapted to engage a part of a railway vehicle.

5 I will describe one form of railway braking apparatus embodying my inventiomand will then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is 10 a view, partly" diagrammatic,illustrating one form of railwaybraking apparatus embodying my invention. 2 is an'enlarged sectional viewtaken. on the line II-II of Fig. 1. Fig. 3 is an enlarged sectional view taken on 15 the line iii-in of Fig. 1.

Similar reference characters refer to simi lar parts each of the three views.

Referring first to Fig. 1, the reference characters 1, and 1 designate the two track rails of a stretch of railway track provided with trachway braking mechanism. In the form here shown, this mechanism comprises two braking bars A. and 13 located on oppo- 5 site sides of the track rail 1, and two similar braking bars A and B located onopposite sides of the track rail 1.. Each braking bar comprises a brake beam- 3 to which a brake shoe 4 is attached by means of a plurality of coil. springs 2. The braking bars for each rail are so associated with the rail that when they are moved toward the rail, the brake shoes will engage the sides of the wheels of a passing vehicle and so'will 'lrictionally re duce the speed of such vehicle. The, coil springs 2 serve to limit the mechanical pressure ot the shoes against the wheels to that w ich the springs, transmit.

The braking cars A, B, A, and B are controlled by a iiuid pressure motor device designated by the reference character C. As here shown, this motor device comprises a cyl nder 8 containing a reciprocable piston 9. llhis piston carries a plunger 10, which is operatively connected with the braking barsthrouo h the medium of link work 7 When the piston 9 is in its left-hand position, as shown in Fig. 1. the brakinft'bars are in their non-brakingpositions. When the piston 9 is driven to its rhyn-hand position in cylinder 8, however, the braking bars associated with each 0-1 the track rails are urged toward the corresponding rail so as to engage the sides of the wheels of a railway vehicle, bars A and B moving upwardly toward the rails, and bars A and B movin downwardly toward the rails, as seen in Fig. 1.

The reference character D designates a magnet valve comprising a valve stem 11 provided with an armature 11 and a winding 12. When winding 12 is energized, the lefthand end of cylinder 8 is connected with a suitable source of fluid pressure not shown in the drawing, through pipe 13, valve D and pipe 14. When winding 12 is de-energized',

however, the valve Dis closed, so that the supply of fluid pressure to the left-hand end of cylinder 8 is discontinued. A second valve E comprises a valve stem 11:, which is also provided with an armature 11 and a winding 12, and is so arranged that when winding 12 is de-energized cylinder 8 on the lefthand sideof piston 9 is connected with atmosphere through pipe 15,- valve E and a port 16. If, however, winding 12 energized, valve'stem 11 is drawn downwardly to blank pipe 15 and prevent the escape of fluid pressure from cylinder 8. A third valve, designated by the reference character F, controls the supply of fluid pressure to the right-hand end of cylinder 8. When winding 12 of this valve is de-energized, pipe 17 communicating with the right-hand end of cylinder 8 is connected with atmosphere through port 16. 'When winding 12 of valve F is energized, however, valve stem 11 is moved downwardly and pipe 17 is disconnected from port 16 and is connected with a source of fluid pressure through pipe 13.

The valve Dis controlled in part by three automatic circuit controllers K, L, and M,

each comprising a pressure'responsive unit 18, such for example, as a Bourdon tube, which controls a contact 19, in such manner that when pressure in the Bourbon tube 18 exceeds a predetermined amount, the contact 19 will be open. T Each of the Bourdon tubes 18 is connected with the left-hand end of cylinder 8 through a pipe 20, but the parts are so proportioned that the circuit controllers K, L,'and M operate at diiierent pressures.

V For purposes of explanation, I will assume that all of the circuit controllers K, L, and M are closed at pressures below 25 lbs. per square inch. At all pressures above 25 lbs. per square inch, circuit controller M is open; at all pressures above 50 lbs. per square inch, circuit controller L is open; and at all pressures above 75 lbs. per square inch, circuit controller K is open.

The valves D, E and F are controlled in part by a manually operable circuit controller N comprising a pivoted lever 26 and a plurality of fixed contacts 22, 23, 24, 25, and 28 which may be selectively engaged by the lever, depending upon its position. The circuit controller N also comprises a contact segment 21, so disposed that when lever 26 engages contacts 22, 23, 24, or 25, the lever will also engage the segment 21. Carried on lever 26 is a push button designated by the reference character 27. This push button is normally closed, but is arranged to be opened manually.

As shown in the drawings, all of the valves D, E, and F are de-energized, and

the piston 9 is in its left-hand position, so

that thebraking bars located in the trackway are in their non-braking or ineffective positions. I will first assume that the operator wishes to make a light brake application. To accomplish this he moves lever 26 into engagement with contact 22. Current then flows from a suitable source of energy, such as a battery P, through wires 29 and 30, push button 27, wire 31, lever 26, segment 21, wire 32, winding 12 of valve E, and wires 33, 70, 34, and back to battery P. Valve E is therefore closed to blank pipe 15 and prevent the escape of fluid from the left-hand end of cylinder 8. Furthermore, current flows from battery P through wires 29 and 30, push button 27, wire 31, lever 26, contact 22, wires 76 and 36, contact 19 of circuit con troller M, wires 37, 38 and 40, winding 12 of valve D, and wires 41, 70, 34, and 35 back to battery P. Valve D therefore opens, and fluid pressure is supplied to the left-hand end of cylinder 8, forcing piston 9, and therefore, plunger 10, to the right, and urging the braking bars into their brake applying positions. It the track rails 1 and 1 are occupied by'a railway vehicle, the brake shoes will engage the flanges of the wheels with a force which depends upon the pressure supplied to cylinder 8. When this pressure reaches 25 lbs. per square inch, the contact 19 of circuit controller M opens, thereby interrupting the circuit just traced for winding 12 of valve D and interrupting the supply of pressure to cylinder 8. If the pressure in cylinder 1 is decreased. as by leakage past the piston 9, to a value below 25 lbs. per square inch, circuit controller M immediately recloses and restores the pressure to the proper value.

Should the operator wish to increase the pressure applied to the braking bars in the trackway to lbs. per square inch, he moves lever 26 into engagement with contact 23. The lever still engages segment 21 and so valve E remains closed. A new circuit for winding 12 of valve D is now closed, however, from battery P through wires 29 and 30, push button 27, wire 31, lever 26, contact 23, wire 43, contact 19 of circuit controller L, wires 44, 38, and 40, winding 12 of valve D, and wires 41, 70, 34, and 35 back to battery P. The valve D is now energized over this new circuit so that fluid pressure is supplied to cylinder 8 until the fluid in the lefthand end of the cylinder reaches 50 lbs. per square inch. Circuit controller L then opens. The pressure in the left-hand end of cylin der 8 is thereafter maintained at the proper value, as explained in connection with circuit controller M. In similar manner, if lever 26 is moved into engagement with con tact 24, magnet valve D is energized over contact 19 of circuit controller K, so that the pressure in the left-hand end of cylinder 8 will then be maintained at lbs. per square inch. The circuit for winding 12 of valve D will then be from battery P, through wires 29 and 30, push button 27 wire 31, lever 26, contact 24, wire 45, contact 19 of circuit controller K, wires 46, 39, and 40, a;

wires 29 and 30, push button 27, wire 31,

lever 26, contact 25, wires 47, 39, and 40, winding 12 of valve D and wires 41, 70, 34, and 35 back to battery P. It will therefore be plain that when lever 26 is in this position, the control of magnet valve D is independent of the pressure existing in cylinder 8 and that the full amount of pressure available in pipe 13 will be admitted to the fluid pressure motor 0 to give a braking force corresponding to this pressure inpipe 13.

T will now assume that the operator wishes to reduce the braking force exerted by the braking bars from a higher to a lower value. To do this he moves lever 26 into engagement with the contact corresponding to the de sired braking force, and then operates push button 27. As a result, the circuit for magnet valve E is opened, which valve immediately opens and vents the left-hand end of cylinder 8 to atmosphere. The operator continues this operation until the pressure in cylinder 8 is reduced to a value correspond.- ing to the desired braking force, after which he releases push button 27. The pressure is then maintained at the proper value in the Ti crates push button 27 until the pressure in cylinder 8 is reduced to 50 lbs. per square inch. Valve D then maintains'the pressure at this value.

If the operator wishes to restore the braking bars to their inefi'ective positions, heiirst moves lever 26 to the position in which it is illustrated in the drawings. All contactsof circuit controller N are then open, so that valve D is closed and valve Eis open.. The

' left-hand end of cylinder 8 is therefore connectedwith atmosphere; The operator next moves lever 26 into engagementv with contact 28. Current then flows from battery P through wires 29 and. 30, pushv button 27, wire 31, lever 26, contact 28, wire. 51, winding 12 of valve F, and wires 71, 34, and back to battery P.v Valve stem 11: of valve F therefore moves downwardly and fluid pressure is supplied to the right-hand end of cylinder 8. Piston 9 is therefore driven to the left, and the braking bars are moved to their non-braking positions. With the braking apparatus thus released, the operator may return lever 26 to the position shown in the drawings, thereby de-energizing; the valve F and restoring the apparatus to its normal condition.

ll ith the apparatus constructed in the manner thus far described, it willbe evident '3 that the braking force exerted by each of the braking bars A, B, A and B isdependent both upon the force transmitted by the springs 2, and uponv the pressure of the fluid in the left-hand end of cylinder 8. It occasionally becomes desirable, however, to

lock the brake beams in one or more predetermined positions in such manner that, if a vehicle enters the braking apparatus, the braking force exerted by the braking bars will be determined entirely by the amount of deformation of thesprings2. To accomplish this result, I have provided locking apparatus designated in general by the reference character J, wiich apparatus locks the link work 7, and therefore the brake beams, in predetermined positions.-

Referring now also to Figs. 2 and 3, the apparatus J comprises a casting. 66 provided with a horizontal slot 64: containing a looking bar 50. The locking bar is connected at its left-hand end, by means of an adjust able operating rod 49, with the plunger 10 of the fluid pressure motor C, and'the bar is provided in its upper face with a plurality of spaced notches here shown as two in number and designated 50 and 50". (Jo-operating with the notches 50 and 50" in the bar 50 is a locking dog 57 extending transvemely across the bar. The dog 57 reciprocates in a transverse slot 7a in the casting 6.6, and

is operated by afluid pressure motor Q. The fluid pressure motor Q comprises a cylinder 61 containing a piston 62 driving a piston rod 63. The piston rod 63 is connected by meansof an adiustable linl: 58, and a fixed link 53, with the lower end of a driving lever 54, which in turn is Keyed to a rockshaft 52. The rockshaft 52 1s 1ournaled 1n the upper ends of two bearing blocks 56 and 56 which are bolted to the upper side of he casting 66. Attached to one end of the roclrshaft' 52 in any suitable manner is a crank 60, the crank pin 65 of which carries a link 59, which is pivoted at its lower end on a'pin 73 extending through a jaw 7 2 formed on the upper side of the locking dog 57. A similar crank is fastened to the other end of the rockshaft 52, and carries on its crank pin a link 59*. The lower end of the link 59 is pivoted on a pin 73 extending through a jaw 72 on the top of the locking dog 57.

The parts of the apparatus J are so proportioned that when piston 62 of fluid pressure motor Q occupies its right-hand posi tion, in which it is shown in the drawings, the dog 57'is drawn upwardly out of engage ment with the bar 50. hen the piston 62 of motor Q, moved toward the left, however, thedog 57 is moved downwardly, and if either of the notches 50 or 50 is in alignment with the dog, the dog will enter the aligned notch to lock the locking bar, and hence the brake beams, against further movement, un til the dog isreleased.

Two valves G and H (see Fig. 1') similar to the valve F previously described, control the supply of fluid pressure to the cylinder 61 of fluid pressure motor Q. When winding 12 of valve G is de-energized, pipe 67, communicating with the left-hand end of cylinder 61 is connected with atmosphere through port 16. When winding 12 of valve G is energized, however, valve stem 11 is moved downwardly and pipe 67 is discon nected from port 16, and is connected with a source of fiuid'pressure through pipe 13. In similar manner, wh n winding 12 of valve H' is ole-energized, pipe 68, communicating with the righthand end of cylinder 61, is connected with atmosphere through port 16, and when winding 12 of valve H is energized, valve stem 11 is moved downwardly and pipe 68 is disconnected from atmosphere and is connected with a source of fluid pressure through pipe 13;

The valves G and H are controlled by the circuit controller N. previously described, and. also by a push button R comprising two contacts 79 and 84. As shown in the drawings, contact 84- is open and contact 79 is the push button is restored to its original position.

lVinding 12 of valve H is provided with a circuit which passes from battery P, through wires 29 and 30, push button 27, wire 31, lever 26 of circuit controller N, con tact 22, wires 76 and 77, an asymmetric unit S wires 77 a and 78, contact 79 of push button R, wire 80, winding 12 of: valve H, and wires 81, 82, and back to battery P. A branch for this circuit passes "from lever 26 of circuit controller N through contact 25, wire 90, asymmetric unit- S and wire 90 to wire 78.- lVinding 12 of valve H is therefore energized when lever 26 of circuit controller N is in engagement with eithercontact 22 or contact 25, provided contact 79 of JLlSll button It is closed.

Winding 12 of valve G is provided with a circuit which passes from battery P, through wires 29 and 30, push button 27, wire 31, lever 26 of circuit controller N, contact 23, wire 42, asymmetric unit S, wires 42 89, and 86, winding 12 of valve G, and wires 87, 82, and 35, back to battery P. A branch for this circuit passes from lever 26 of circuit controller N, through contact 24, wire 88, asymmetric unit S and wire 88 to wire 89. Winding 12 of valve G is also provided with another circuit which passes from battery P, through wires 29 and 83, contact 84 of push button R, wires 85 and 86, winding 12 of valve G, and wires 87, 82, and 35, back to battery P. It will be apparent, therefore, that winding 12 of valve G is energized. when lever 26 of circuit con troller N is in engagement with either of contact 23 or 24, or when push button R is reversed so that contact 84 is closed.

In explaining the operation of the apparatus as a whole, i will assume that notches and 50 are located in the locking bar 50 in such manner that when notch 5O falls into alignment with the dog 57, the braking bars will exert a minimum bra-king force, which is less than that which can be obtained with the lowest pressure available in the left-hand end of cylinder 8 of fluid pressure motor C, and that when the notch 5O tells into alignment with the dog 57, the ra ing bars will exert a maximum braking force which is greater than that which can he obtained with full line pressure in the left-handend of cylinder 8 of fluid pressure motor C. It is to be understood, however, that t isparticular location of the notches is not essential to my invention and may be varied as conditions may demand.

Nit/h the apparatus arranged in this manner, if the operator wishes the braking bars to exert the minimum ln'aking force, he moves lever 26 of circuit controller N into engagement with contact and operates push button R to close contact 79 unless this contact is already closed. The windings 12 of valves D and E are then energized over the circuits previously traced for these windings, and fluid pressure is admitted to the left-hand end of cylinder 8 of fluid pressure motor C until the'pressure reaches 25 pounds per square inch, the 'eby driving piston 9 toward the right. Since lever 26 is in engagement with contact 22, and since contact 79 of push button It is closed, winding12 of valve H is also energized, and fluid pressure is admitted to the right-hand end of cylinder 61 of fluid pressure motor so that piston 62 is driven toward the left and the dog 57 is urged into engagement with the locking bar 50. As a result, when piston 9 of fluid pressure motor C has moved to the right far enough to bring notch 50 in the locking bar 50 into alignment with the dog 57, the dog enters the aligned notch and holds the locking bar, and hence the brake beams, against further movement in either direction until the dog is released. It a vehicle then enters the braking apparatus the braking bars will exert the minimum desired braking force. It will be noted that this braking force is dependent entirely upon the deformation of the springs 2, and is not dependent upon the pressure of the fluid in the left-hand end of fluid pressure motor G.

It, now, the operator reverses push button R, contact 79 is opened and contact 84 is closed. As a result, winding 12 of valve H is die-energized and winding 12 of valve G is energized, so that fluid pressure is ad mitted to the lett-hand end of cylinder 61 of fluid pressure motor Piston 62 of fluid pressure motor Q, is therefore driven toward the right and dog 57 is withdrawn from engagement with the bar 50. The locking apparatus therefore has no eflect on the braking apparatus, and if lever 26 of circuit controller N is allowed to remain on contact 22, the braking bars are urged toward the rails by a pressure of 25 pounds per square inch on the left-hand side of piston 9.

If the operator wishes to increase the braking force exerted by the braking bars to that corresponding to a pressure of .50 or 75 pounds per square inch in the left-hand end of cylinder 8 of fluid pressure motor 0, he moves lever 26 of circuit controller N into engagement with contact 23 or 24, respectively. Fluid at a pressure of 50 or 7 5 pounds per square inch is then admitted to the lefthand end of cylinder 8 of fluid pressure motor C, depending upon whether lever 26 engages contact 23 or 24, and the braking bars are urged into their brake applying positions by a corresponding pressure as described hereinbefore. It dog 57 is in engagement with looking bar 50 when lever 26 is moved into engagement with contact 23 or contact 24, the dog will be automatically withdrawn because, as was previously pointed out, when lever 26 of circuit controller N engages either of these contacts, winding 12 of valve H is de-..ener-gized and winding 12 of valve G is energized, so that fluid pressure is admitted to the left-hand end of cylinder 610i fiuid pressure motor Q and piston 62- is driven toward the. right. Under these conditions, therefore, the locking apparatus has noetlect on the braking apparatus, and the braking bars will exert .a braking forcecorresponding to the pressure in the left-hand end oi cyline I gized andwin'ding 12 of valve H is de-ener gized so that dog .57 is heldout of engage.- ment with the locking bar 50. The locking apparatus therefore ia's no effect upon the brakingapparatus, and thebraking bars are urged toward the rails by the pressure in the 1' held in its proper position.

left-hand end of cylinder 8.

if, now, the operator wishes the braking bars to exert their maxi-munrbraking force, he operatespush huttcn R to close contact 79", and closes Contact 2625 of circuit controller Piston 9 of fluid pressure motor G is therefore driven toward the right by full line pressurein the left-hand end of cylinder 8. Since the circuitisnow closed' for wind? ing- 12 of valve H, dog 57 is urged into engagement with the locking bar 5,0, and when notch .50 moves into, alignment with thedog 57, the dog enters the notch and holds the locking bar in theposition which itthen o.ccu-. pies. It should be noticed that if the piston 9 occupies its extreme lett-hand osition when the operator wishesto attain the maxi: mum braking force, he must reverse the push button R to withdraw the dog 57 until the locking bar has moved iar enoug-hrto the right so that the dog will not engage notch 50 He may then restore the push button R to the position in which contact 7 9 is closed so that when the notch 50 falls into alignment with the dog the locking bar will be If a vehicle enters the braking apparatus with the dog 57 in the notch 50% the braking force exerted against the vehicle is dependent solely upon the amount of deformation of the springs 2,

and I prefer to proportion the apparatus so reducet-he .bralringiforce exerted .byithe bra-kingFhars from aihigher to a lower value,zor'to returnthe braking. bars to their inefi'ective positions, he first makes sure that dog .57 is H withdrawn from engagement With locking '50.- hy operating push :button to close contact 84 and open contact 179.. :He then operates;acircuit controller N to. supply ithe proper pressure tothe left+hand end .ofcyle zillder {hie advantage of apparatus embodying iny' invention is that by-the use ofthe looking apparatus (La larger braking force .may be obtained than a given line )pr'essureiand size of cylinder ipermit without this apparatus. T he reason forthis is that without thelocking apparatus, .a entering the retarder will notonly compress the springs'2, but 'Willal-so move the'brake iheam-s 3 away -from'the rails because piston'9' can move back a short, dis.-

tance in cylinder 8:, :andthis reducesthe. force exerted by the springs. on the car wheels; whereas, when'the locking device is used the brake beams 3 arclheld fixed in position and 7 so the force exerted by thespringsflis, in: creased.

j Another: advantageof apparatus embndy= ing invention is that when a very light vehicle isnt'o bezretanded, the brake beams may beilooked in .aposition in which'theibraking force exertedby the braking bar-sis suflioient to 'retard the vehicle but isfnot suificientyto derail the vehicle. This braking force is difficult to obtainaby controlling the pressure of thefluidin the Zleftehandend of cylin: dcrz8of fluid pressure motor-C because ofthe friction between the various parts of the mechanism.

too

Nhile I have. shown only two notches 50. w

have herein shown and de-.

1. Railway braking apparatus comprising a brake beam, a brake shoe, means for iyielde ably attaching-said shoe to saidbeam, a first fluid pressure motor having its plunger-ope. eratively connected with saidbeam, meansfor selectively controlling the supply of fluid pressure to saidifirs-trmotonz a locking 'har operatively connected withrthe plunger ofsaid first: motor and provided in .itsupper face with a plurality of notches, .a lock-ing' dog, a second fluid pressure imotor :operativ'ely con-. nected withsaid dog, means for atti-me's sup-.

6 neeaevs plying fluid pressure to one end of said second motor to cause said dog to enter a selected one of said notches in said locking bar, and means for at other times supplying fluid pressure to the other end of said second motor to cause said dog to be withdrawn from an occupied one of said notches.

2. Railway braking apparatus comprising a brake beam located in the trackway, a brake shoe, means including a plurality of springs for yieldably attaching said shoe to said beam, a first fluid pressure motor for actuating said beam, a first Winding controlling the admission of fluid to said first motor, a second winding controlling the exhaust of fluid from said first motor, a series ofnormally closed contacts arranged to open successively as the pressure in said motor increases, a manually operable circuit controller, a circuit for said second winding controlled by said circuit controller, a plurality of circuits for said first winding controlled by said circuit controller and each including one of said contacts, a locking bar also actuated by said first fluid pressure motor and provided with a plurality of notches, a locking dog, a second fluid pressure motor for operating said dog, and means also controlled by said circuit controller for supplying fluid pressure to said second motor for at times urging said dog into one of said notches and for at other times withdrawing said dog from one of said notches.

8. Railway braking apparatus comprising a brake beam located in the trackway, a brake shoe, a plurality of coil springs, means including said coil springs for attaching said shoe to said beam, a first fluid pressure motor having its plunger operatively connected with said beam, a locking bar connected with the plunger of said'first motor and provided with two spaced notches, a casting provided with a horizontal slot receiving said bar, a locking dog extending transversely across said bar in a slot in said casting for at times entering one of said notches in said locking bar to prevent movement of the beam in either direction, a jaw integral with said locking dog on its upper sides, a pin extending through said jaw, a link pivoted on said pin, abearing block attached to the upper side of said casting, a rockshaft ournaled in the upper end of said bearing block, a crank fastened to said shaft and having its crank pin journaled in the upper end of said link, a driving arm keyed to said shaft, a second fluid pressure motor operatively connected with said arm in such manner that said dog is moved into or out of engagement with said locking bar depending upon whether the piston of said second motor is driven to the left or to the right, a first winding for controlling the admission of fluid to said first motor, a second winding for controlling the exhaust of fluid from said first motor, a third winding for controlling the admission of fluid to one end of said. second motor, a fourth winding for controlling the admission of fluid to the other end of said second motor, and a manually operable circuit controller for controlling the supply of energy to each of said windings.

4:. Railway braking apparatus comprising a brake beam located in the trackway, a brake shoe, means including a plurality of springs for yieldably attaching said shoe to said beam, a first fluid pressure motor for actuating said beam,-a first winding controlling the admission of fluid to said first motor, a second winding controlling the exhaust of fluid from said first motor, a series of normally closed contacts arranged to open successively as the pressure in said motor increases, a manually operable circuit controller, a circuit for said second winding controlled by said circuit controller, a plurality ofcircuits for said first winding controlled by said circuit controller and each including one of said contacts, a locking bar also actuated by said first fluid pressure motor and provided with a plurality of notches, a locking dog, a second fluid pressure motor for operating said dog, a push button, and means controlled by said circuit controller and by said push button for supplying fluid to said second motor for at times urging said dog into one of said notches and for at other times withdrawing said dog from one of said notches.

5. Railway braking apparatus comprising a brake beam located in the trackway, a brake shoe, means including a coil spring for yield ably attaching said shoe to said beam, a fluid pressure motor for actuating said beam, a manually operable circuit controller, means including said circuit controller for selectively controlling the fluid pressure supplied to said motor, a push button, a locking bar operatively attached to said brake beam, and

means controlled by said circuit controller and by said push button for at times locking said locking bar in a selected one of a plurality of positions.

In testimony whereof I affix my signature.

CHARLES E. BURNS. 

